r - What does the error "arguments imply differing number of rows: x, y" mean?

Question

I'm trying to create a plot from elements of csv file which looks like this:

h1,h2,h3,h4
a,1,0,1,0
b,1,1,0,1
c,0,0,1,0

I tried the following code but am receiving an error saying

Error in data.frame(id = varieties, attr(mat, "row.names"), check.rows = FALSE) : arguments imply differing number of rows: 8, 20

My sample data has 8 columns and 20 rows (excluding header and row names). I tried to look up online and tried to implement a few fixes but the issue still persists. I'd really appreciate any help.

mat <- read.csv("trial.csv", header=T, row.names=1)
varieties = names(mat)
df <- data.frame(id=varieties,attr(mat, "row.names"), check.rows= FALSE)

Answer 1

Your data.frame mat is rectangular (n_rows!= n_cols).

Therefore, you cannot make a data.frame out of the column- and rownames, because each column in a data.frame must be the same length.

Maybe this suffices your needs:

require(reshape2)
mat$id <- rownames(mat) 
melt(mat)